I want a procedural texture on a PNG "Decal". How do I set up the nodes?
The Principled Shader is configured with 100% roughness for pure black diffuse with no specular. This will basically produce black regardless of the angle of the incoming light - the 100% roughness on the black surface will basically kill all bumps and textures and simply render as black.

To address this reduce the Roughness and add some Specular to provide some shine to the bumps. 

In addition, the Noise fed directly into the Normal Map will be producing incorrect normals (the output of the noise is not a proper basis for a normal map - it will be in a random direction (so may point ‘inwards’) and it’s length will not be 1). Better to feed the Fac of the Noise into a Bump node instead, to generate the surface normal.